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Patented Aug. 20, 1935 I q 12312233 V .I'PURIFICATION 0F ntru emo. NTIIR ElJm E n w na-asmh;awake; Apia-its T B bFM m S erwood wi aas igno to E- I V du Pont-ddNm urs & obmpany, ,Yllilmington, i I

Belg, a ciirporatipnjof Delaware N met-hylil-bromo-anthrapyridone :and more particularly to :llhe purification of 5 this product and the separation therefrom of those impurities which ingthei subsequent condensation with the arylaminesiproduce blue-color bodies.

In the preparation of l-N-methyl-l-bromo anthrapyridone there is generally present in the resulting product some l-methyl-aminoA- bromo-anthraquinone. While the condensation of l-N-methyl-4-bromo-anthrapyridone with an arylarnine, such as para-toluidine, and sulfonation of the resulting color base produces 'red wool dyestuffs, the condensation of the same arylamine with l-methyl-amino-4-bromo-anthraquinone produces a bright blue. dyestuff. Even very small amounts of l-methylaminol-bromoanthraquinone as an impurity in the l-N-methyl- -bromo-anthrapyridone consequently give a final dyestuif which is materially bluer in shade than pure 1-N-methylr-para-toluido-anthrapyridone sulfo acid.

It is therefore an object of our invention to provide a process for purifying l-N-methyl-lbromo-anthrapyridone and for eliminating substantially all of those undesirable impurities which tend toialter the shade of the final dyestuff to be prepared therefrom.

We have found that the crude l-N-methyllbromo-anthrapyridone may be dissolved in concentrated sulfuric acid and precipitated therefrom by carefully diluting with water or dilute acid to an acid concentration of from to while the undesirable impurities remain dissolved in the acid solution. This method is particularly suitable for use in conjunction with the purification of the crude 1-N-methyl-4-bromo-anthrapyridone by the nitrite treatment, which is disclosed more fully in copending application Ser. No. 749,477, and illustrated in the following examples.

The following examples are given to more fully illustrate our invention. Parts used are by weight.

Example 1 50 parts of crude l-N-methyll-bromo-anthrapyridone are dissolved in 500 parts of 93% sulfuric acid. When solution is complete, after about one hour, 95 parts of water are slowly added over one hour, care being taken that the temperature does not rise over 80 C. After the addition of the water is completed, the mass is stirred at room temperature for eight to twelve hours more. The acid suspension is then filtered and washed with parts of 60 B. sulfuric acid 'fl w m pplication.October.:22, 1934,

v r al..N 149,479, V .l J

a ian; This; inyention relates. .to; the; preparation Gill:-

- acid are mixed. with 100 parts of 93% sulfuric and sludge d in 500 partsiof. hot water. -'1l1e .11 .,.j" cipitate is, filtered,.,washed acid free: anddried. 1

1 Br id? "l5 parts of sodium nitrite areadded 't'o'j 500 "'5 parts of 93% sulfuric acidat a temperature be low "30 C. with good agitation. 100 parts of crude 1 N-methyl--bromo-anthrapyridone are then added to the acid solution and the mixture heated to 80 C. ,over a period of one-half hour 10 and held at 8082 C. for a period of about three hours. 96 parts of water are then added slowly, maintaining thetemperature at 90 C. When all the water has been added, the mass is cooled to room. temperature and agitated at this temperature for several hours, filtered at 20 to 30 and washed with 100 parts of 78% sulfuric acid, sucked dry and sludged in 1,000 partsof hot Water. The yellow precipitate is filtered off,

washed acid free and dried at 100 C. 20

Example 3 parts of a 5% solution of nitrosyl sulfuric acid. 50 parts of crude 1-N-methyl-4-bromo- 5 anthrapyridone are added at 30 C. and the reaction mass heated to 75 C. over a period of onehalf hour. The temperature is held at 75 for four hours. 100' parts of water are added slowly over a period of one hour at a temperature of 80 C. The mass is cooled to 30 C. andheld for eight hours. The precipitate is filtered o-fi, washed with 50 parts of 70% sulfuric acid, sucked dry and sludged in 2,500 parts of hot water. The purified 35 1-N-methyl-4-bromo-anthrapyridone is filtered, washed acid free and dried.

While in the above examples we have described the dissolving of the anthrapyridone compound in 93% acid and the precipitation from an acid 40 solution of about 78%, the separation may also be eifected by heating a finely dispersed crude anthrapyridone in 78% acid, cooling the suspension to room temperatures and filtering. The concentration'of sulfuric acid at the time of fil-'- 45 tration may vary between 70v and 80%, although the use of about 78% acid is preferred. The mass may be filtered at temperatures somewhat higher or lower than those given in the specific examples, depending on the particular acid concentration 50 used. Temperatures from 20 to 30, however, are preferred. While concentrated sulfuric acid of above.93% may be used to effect the solution of the anthr-apyridone compound, care must be exercised in the use of the moreconcentrated 55 acids to avoid sulfonation of the anthrapyri-done compound. The quantity of acid used may vary within wide limits. The use of from 4 to 20 parts of acid per part of the 1-N-methyl-4-bromo-anthrapyridone has been found to give satisfactory results."" 3 v i a The corresponding "1-N-methyl-4-chloro-anthrapyridone compound may be prepared in a similar manner to that described above.

What we claim is:

'1. In the preparation of 1-N-methjrl-4-halogen-anthrapyri-done, the step which comprises precipitating the 1-N-methy1-4-halogen-anthrapyridone from a sulfuric acid solution by bringing the concentration of the acid to about '70 to 2. In the preparation of l-N-methyl l-halo-r .7 gen-anthrapyridone, the steps which comprise precipitating 1-N-methyl-4-halogen-anthrapyridone from a sulfuric acid solution by bringing the concentration of the acid to about to andseparating the precipitate fromthe' solution at a temperature of from 20 to 30 C.

3. In the preparation of l-N-methyli-bromoanthrapyridone, the step which comprises precipitating the 1-N-methyl-4-bromo-anthrapyril temperature of from 20 to 30 C.

5. In..the preparation of 1-N-methy1-4-bromoanthrapyridone, the steps which comprise precipitating 1-N-methy1-4-bromo-anthrapyridone from a sulfuric acid solution by bringing the concentration of the acid to approximately 78% and separating the precipitate from the solution at room temperature.

6. In the preparation of l-N-methyli-bromoanthrapyridone wherein the resulting crude prodv not is treated with nitrous acid in a sulfuric acid solution, the steps which comprise bringing the concentration of the acid to about '70 to 80% to precipitate the 1-N-methy1-4-bromo-anthrapyri done, and separating-it from the solution at 20 to 30 C.

a HENRY-R. LEE. 'EDW'IN C. BUXBAUMW- 

